Whumps and noisey operation isn't the norm for any system,they are making excuses. How long could a company expect to stay in business if their product was annoying?

sizing seems to be a question plus quality of install..noise totally not acceptable...

IMO

Gentlemen,

The location is ARIZONA.

Sizing rules are different.

Hmmm, 28 BTU per square foot. This could be a new record for the forum.

Well...dammit.

Gentlemen: The location is ARIZONA. Sizing rules are different.

Well, yes and no, I saw that and they don't have a humidity issue (as a rule) but 3.5 tons for 1500 sq ft sounds oversized to me. what size was the previous unit?

In any event, the OP has real problems.

If you want some additional feedback then try posting your question in this HVAC contractor forum.

Believe it or not, the old unit was 5 tons, it was always a "blast" when it came on! Monsoon rains raise the humidity, but otherwise we hang out between 30-40%. The 5gal bucket under my condensation pipe fills everyday.

The problem with Arizona and other desert like conditions is lack of humidity. So in many places with arid type temps they use what are called 'swamp coolers'.

I have never seen a swamp cooler, much less want to see one. I'm pretty sure you would know if you had one or not... as they mist water into the air... to increase humidity.

Problem with air conditioning only option for this climate (HOT) is that capacity (rated tonnage) of equipment goes down. equilibrium for R410a is around 95 degree OAT as this picture shows.

So in other words... The HVAC market is not a 1 size fits all market. The outdoor LOAD is the biggest load you have to over come.

If you are hitting 115 degree (air temp) your 3 ton condenser is at best running like a 2.5 ton. At 95 OAT, depending on 'Entering Wet Bulb' (EWB) temperature and indoor fan speed it runs closer to a 3 ton unit.

36.0 = 3 ton

30.0 = 2.5 ton

24.0 = 2 ton

This is why when you ask questions on this board we ask for location. No two locations are alike. UNLESS, they are across the street from one another. Ok, the world is small, but not that small... Science.

The humidity levels in the Phoenix area are higher then most people think. This is because people want to see green landscapes and will water on a daily basis to keep the plants alive in a desert.

The idea of installing the biggest air conditioner that will fit in a house is old school. AC designers need to do load calculations just like other installers.

Thanks all, then what is a good question I can ask the installer to get them out one more time? I've asked if the noise is normal = yes (grrrr). I also had them out because vibration was shaking a ceiling fan, they installed 2 pads (isul?) and that worked. I feel like the unit should be quieter on start up AND blow softer and maybe longer if that makes sense. I'd like to ask an intelligent question, or at least fake it...

You have a few problems working against you.

1. Package equipment is best suited for commercial roof top or along side of building with duct lead off thru the walls or roof top.

2. When it comes to rooftop installations Commercial roof tops can be 30 feet tall / noise typically doesn't matter as much. (you're not there to sleep.)

So these problems could be the reason for it. Package units tend to be a bit noisy.

Quiet is a non describable term in HVAC world, because any unit while running will make 'some' noise.

Soft blow versus hard blow can be a combination of duct work and blower speed up to including the size of the unit. (A larger unit requires more air.)

Your 3.5 ton needs about 1400 CFM of air. If your duct system can not handle this air flow this can cause not only noises but also detrimental system problems. (Excessive Static Pressure). Can cause the unit to shake, in some cases violently depending on how bad the problem is.

Mounting the package unit to the roof. Anything that vibrates will cause noise. If this noise (vibration) comes in contact with various structure related parts it will travel the lengths of these structure parts and more or less have an echo type effect through out the structure in the worst cases.

Probably overthinking here. Original problem a loud thump on startup. Possibly just ductwork thumping under pressure. Possibly fan speed is set too high. Usually the default set is max and they didnt adjust it. If fan speed cant be adjusted, perhaps they can stretch or brace the ductwork so it doesnt thump.

Just a couple notes and then I'll sign off this thread. The old 5 ton unit didn't make this noise on start up. Almost all the houses in town have rooftop units. The duct work is 'static', it is galvanized metal so I can see how that sound is traveling thru the attic and into the house. I'll ask about the fan speed, thank you! I appreciate all of your time and information very much - e.

Also my 2 cents. I'm born & raised in Phoenix. For some reason, most ACs are on the roof. They turn them sideways and put them in the ceiling area. Phoenix isn't big on basements or attics so that's what they came up with.

I thought it was like that everywhere til I moved to Ohio. Here the only AC units on roofs are commercial.

Package units are easier to replace. Given the heat in Phoenix who would want to spend any time in one of those attics?

Package you just pop off the package, replace it with the new package, hook up ductwork, electrical, drain runs, gas connection if any and you're done. No refrigerant work, no brazing etc.

Typically in exchange for that the technicians know very little about high level problems. Because every job they go to -- it's pop off and replace one box for another.

This post isn't a knock to people who do this kind of work (I was once there myself in another life time ago). You have to start somewhere and I am merely trying to suggest how and why the OP is having to deal with a problem such as this and quite possibly how hard it may be to find a solution.